1. Field of the Invention
The present invention relates to a display device, and more particularly, to a panel display device and a method for forming a protective layer within the same in which a flat type panel display device is formed using organic electro-luminescence (EL).
2. Discussion of the Related Art
Generally, organic light-emitting diode (OLED) is very susceptible to the atmospheric gas. Accordingly, if the OLED is exposed to the atmospheric gas, lifetime is reduced. Particularly, an organic EL layer in a panel display device may be oxidized if it is exposed to the atmospheric gas. This is because that the organic EL layer is active to the moisture or O2. Likewise, electrodes such as cathodes or anodes are likely to be oxidized if they are exposed to the atmospheric gas. An oxide is produced between the electrode surface and the organic EL layer due to oxidation of the electrodes. In this case, a problem arises in that the oxide causes leakage and short in the display device.
In this respect, Mg—Ag and/or Al—Li has been used to improve efficiency of an organic EL element. However, problems such as edge shorting, dark spot and decrease of a luminescent area still exist in that Mg—Ag and Al—Li are more susceptible to O2 in the air.
To solve such problems, a device of a sealing structure has been required, which does not allow gases in the air to cause oxidation or deformation of an organic EL layer and electrodes.
The sealing structure is generally formed by either a method using silicon oil and resin or a film formation method.
The method using silicon oil and resin has been used for sealing of an inorganic EL element and is applicable to OLEDs. If this method is used for OLEDs, a solvent of silicon oil and resin is permeated into the organic EL layer and the electrode surface, thereby degrading luminescence characteristics and efficiency.
The film formation method is to form a protective layer outside an organic EL element which is laminated, using a physical vapor deposition (PVD), a chemical vapor deposition (CVD), a plasma enhanced CVD (PECVD), or sputtering. In the film formation method, electrical resistance, rupture strength, and moisture resistance serve to prevent an organic EL layer and electrodes from being oxidized or deformed.
In the aforementioned related art sealing structure, when the organic EL element is driven, it is likely to be damaged by a small content of O2 or moisture (e.g., 1 ppm). For this reason, luminescence characteristic and efficiency of the display device are degraded.